the problem is that thin 2mm spindle is difficult to couple, and in other cases 2mm rods are needed as bearings.
how do you go about
coupling the thin 2mm motor spindle/shaft say to a gear or pulley? or perhaps do you use any mechanical coupler? the rods are so thin and smooth won't it slip?
the other case is where you have gears or pulleys and say 2mm rods. so at its axis perhaps you want it to be coupled to the gear non-moving. but at the supports you want it to be a bearing. i.e. as little friction as possible.
e.g. think of a gear box
how do you go about doing that? i.e. in one case you want that same rod to be coupled (say with the gear or pulley) and the other end you want it to move and hence that would be a bearing
I would expect those pulleys intended for a 2mm shaft to be a tight push fit on the shaft. Certainly the cheap gears that I have are at no risk of slipping on 2mm shafts.
thanks i've ordered some of those plastic pulleys and motors and i'd try the same.
i'm thinking if after all adhesives such as super glue (cyanocrylates) are after all needed
on youtube there are those who simply friction fit the pulleys or gears, as well as those who literally super glue them
just an update, i've got my 'toy' motors and the plastic pulleys as ordered from ebay (1st post)
i tried fitting a small plastic pulley onto the 2mm motor shaft.
Surprisingly the small plastic pulley did a rather firm friction fit on the shaft, it doesn't seem to slip but i'd guess it works ok for low torque applications.
it seemed apparently to me that the plastic pulley shafts are deliberately made smaller perhaps 1.8mm rather than 2mm so that it creates a rather tight fit on the 2mm steel shaft. i'm not sure about the exact dimensions though
no glue or adhesives used
a_g123:
just an update, i've got my 'toy' motors and the plastic pulleys as ordered from ebay (1st post)
it seemed apparently to me that the plastic pulley shafts are deliberately made smaller perhaps 1.8mm rather than 2mm so that it creates a rather tight fit on the 2mm steel shaft. i'm not sure about the exact dimensions though
no glue or adhesives used
Injection molded plastic shrinks as it cools and ages as the polymers become more intertwined and shrink in length.
Paul_KD7HB:
Injection molded plastic shrinks as it cools and ages as the polymers become more intertwined and shrink in length.
Paul
i think the plastic pulley (and possibly gears) is deliberately made with smaller holes than 2mm so that they press fit with the 2mm motor shafts. it seemed very much that way. what i'd think is that these plastic pulleys and gears are after all used in real circumstances and are hence mass produced. i.e. we do not know who is the manufacturer using the parts but that those are produced and sold as general merchandise by 3rd party vendors, when in fact it could be parts of some products - possibly toys or more than that. they may be value buys if one just wants to get some pulleys or gears along with those small 'toy' motors. they may be literally 'more than toys' after all.
what i read somewhere in addition is that press fit plastic parts tend to loosen over time as plastic / polymers tend to creep significantly unlike metals. so initially the press fit is really good, the friction is good and it won't slip. but over time say months they may loosen.
but 2mm shafts with those 'toy' motors are literally hard to work with due to their tiny sizes, and i'd think press fit is also simply part of the industrial design as they are low cost in manufacture (no glue, just press fit) and quick to make them.
the known effect of loosening over time is probably a deliberate design compromise. i.e. it is known that they would loosen over time, but that initially the fit is good and cost is low for the products
given this rather wild assumption, it means that if one decides to make some plastic parts e.g. pulleys
one could literally use similar methods e.g. to make drill holes smaller than the actual motor shafts diameter and press fit them together - without glue ! the hard part as compared to those ready made pulleys and gears sold is that you need to choose the correct plastic (i think acrylic will crack instead) and it may take one some trial and error to determine how much smaller can the hole be to press fit the pulley or gear to motor shafts so that they simply fit together without glue and yet they can take some torque !
this is quite a good news for diy makers meddling with arduino and the like, you can buy these little motors, and pulleys or gears and make small actuators out of them and the costs are rather low based on current ebay ads
If you have a set of drills that vary in 0.1mm steps then you can easily experiment to find the size of hole that gives good grip. You can also use the drills as GO / NO-GO gauges to measure the size of existing holes.